If you have a pencil shaven down a tiny bit, it's damn near impossible to snap. But a brand new full-length pencil is much easier to break. The same physics applies to long legs. Tall lanky basketball players certainly have long legs. If you also take into account their heavyset weight and the force of coming down from that height, it's not as surprising seeing that his bone snapped.

Stress injuries in the legs, feet, and ankles are relatively common in basketball (though this is a statistical outlier in terms of severity).

By the way, for those brave enough or just interested in seeing a more gruesome (but still reasonably viewable) injury, here ya go: /watch?v=plvKlnguJVE
> Warning: Involves the severing of a major artery, where blood is seen spewing on a hockey rink for several seconds. If you're stomach-queasy or blood-repulsed, don't watch.

Surprisingly, player Clint Malarchuk was saved by a head trainer who sealed the severed artery with his bare fingers as soon as he got there, just plugged 'em in there. His decisiveness and knowledge ultimately saved the dude's life. Malarchuk eventually recovered and got out well. Not sure about the several reported heart attacks in the audience though...

Well if he had brittle bones than it wouldn't be that unlikely, would it? Oh, and I meant highly unlikely for someone without brittle bones; sorry for lack of specification. Its likely for someone with that.